Surgery of the eye requires instruments that are small and fine to act through openings of small size and on organs or tissue that are likewise of small size.
Certain tweezers of this type are made from two metal blades that are hinged together in their middle portions or close to their active ends. The precision of the active ends of tweezers of this type depends on the care with which they are fabricated, and in particular on the slack that exists in the hinge. Furthermore, in use, this slack increases and precision decreases.
There also exist tweezers that are made from flat blades that are curved perpendicularly to their thickness and that are united at their ends remote from their active ends. The stiffness of the arms formed by the blades is generally not satisfactory, and the practitioner does not have sufficient feel when handling the tweezers.
Reducing the costs of fabricating this type of equipment is a constant preoccupation for manufacturers, particularly since single use is preferred over multiple use with sterilization after each use. Microsurgery tweezers have thus appeared on the market that are made of plastics material, but that do not give satisfaction insofar as the active portions of the tweezers are lacking in fineness and hardness. Proposals have therefore been made for composite tweezers in which the active portions are made of two metal points with a single piece of plastics material molded thereover to act both as the grip or handle portion of the tweezers and to move the points apart from each other resiliently. The greater or smaller flexibility of such tweezers is determined by the plastics portion, and is not stable over time. The plastics material is subjected to severe treatments by the sterilization procedures to which the tweezers are subjected, thereby accelerating aging thereof and causing its qualities to degrade quickly.
Another drawback of that type of equipment is that plastics material does not make it possible to guarantee that the active points of the tweezers are properly aligned when they move towards each other. It is therefore necessary to incorporate special centering means in the metal portions of the tweezers such as a stud being engaged in a hole, each formed in a respective one of the branches of the tweezers.
Finally, there exist tweezers in which the arms comprise the two branches of a U-shaped pin cut out from a metal sheet, each of the arms then being fitted with a handle against which the fingers of the surgeon press. One of the advantages of such tweezers lies in the precision of manufacture that can be obtained at low cost. The working points or hook-shaped tips are themselves reworked so as to refine their ends, regardless of whether they are in line with the arms, i.e. in the plane of the metal sheet (points) or are curved out from said plane (hook-shaped tips), i.e. raised from the plane of the metal sheet. Nevertheless, it is found that it is still necessary, as with other prior art tweezers, to guide the points or hook-shaped tips so that they coincide exactly when the tweezers are closed.
In tweezers obtained by cutting out, there is not enough metal in each branch for that to be achieved.
The present invention seeks to propose tweezers in the form of a U-shaped metal pin obtained either by being cut out from metal sheet or by the metal injection molding (MIM) technique, the tweezers being fitted simply with means that enable their working points to coincide accurately when the surgeon handles the tweezers.